At present, as IP (Internet Protocol) telephones become widespread, facsimile machines that perform facsimile communication via an IP network has appeared in addition to conventional G3 facsimile machines that use a telephone network. The facsimile communication via the IP network is performed according to various systems including an assumed voice system, a real-time system (the ITU-T.38 system), and an e-mail system (the ITU-T.37 system).
Various techniques to prevent leakage of important information such as confidential information to the outside due to an improper transmission have been proposed about facsimile communication. For example, there is a technique to make a user input a telephone number of a destination twice.
For facsimile communication according to the real-time system mentioned above, a technique to prevent a sender from transmitting a facsimile to an unintentional terminal has been proposed (see PTL (Patent Literature) 1). When an alternative address of a destination address has been notified from an SIP (Session Initiation Protocol) server, the technique interrupts communication and limits a facsimile transmission to the alternative address. When the above-mentioned alternative address notified corresponds to a predetermined permission address, the technique permits communication and the facsimile transmission to the alternative address.
For an e-mail, in order to prevent leakage of important information to the outside due to an improper transmission, a technique to limit a transmission of an e-mail to a destination address according to a domain of the destination address is proposed (see PTL 2).
Incidentally, a telephone number converting apparatus with a function to convert a telephone number into a network address is known conventionally. When a facsimile transmission in the real-time system is performed using this telephone number converting apparatus, a telephone number of a transmitting destination is inputted first and the telephone number converting apparatus is requested to convert the inputted telephone number into a network address. And a facsimile transmission is performed by using the network address acquired from the telephone number converting apparatus as a transmitting destination.
However, even if the above-mentioned conventional techniques are adopted, a facsimile may still be transmitted to an unintentional terminal. The following case can be assumed. That is, even if a correct telephone number is inputted first, a network address registered into the telephone number converting apparatus corresponds to an unintentional terminal and an alternative address is not set. In such a case, a facsimile is transmitted to the unintentional terminal.
Conventionally, although it has been known that the image data received using the real-time system is transferred, a facsimile transmission is not limited based on the network address designated as the transmitting destination of the image data. Accordingly, the image data may have been transmitted to a terminal that is not intended by a user.